<meta charset="utf-8">
(#) NoOp Code

!!! WARNING: NoOp Code
   This is a warning.

Id
:   `NoOp`
Summary
:   NoOp Code
Note
:   **This issue is disabled by default**; use `--enable NoOp`
Severity
:   Warning
Category
:   Correctness
Platform
:   Any
Vendor
:   Android Open Source Project
Feedback
:   https://issuetracker.google.com/issues/new?component=192708
Since
:   8.1.0 (July 2023)
Affects
:   Kotlin and Java files
Editing
:   This check runs on the fly in the IDE editor
Implementation
:   [Source Code](https://cs.android.com/android-studio/platform/tools/base/+/mirror-goog-studio-main:lint/libs/lint-checks/src/main/java/com/android/tools/lint/checks/NoOpDetector.kt)
Tests
:   [Source Code](https://cs.android.com/android-studio/platform/tools/base/+/mirror-goog-studio-main:lint/libs/lint-tests/src/test/java/com/android/tools/lint/checks/NoOpDetectorTest.kt)

This check looks for code which looks like it's a no-op -- usually
leftover expressions from interactive debugging, but in some cases bugs
where you had intended to do something with the expression such as
assign it to a field.

(##) Options

You can configure this lint checks using the following options:

(###) pure-getters

Whether to assume methods with getter-names have no side effects.
Getter methods (where names start with `get` or `is`, and have non-void return types, and no arguments) should not have side effects. With this option turned on, lint will assume that is the case and will list any getter calls whose results are ignored as suspicious code.

Default is false.

Example `lint.xml`:

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~xml linenumbers
&lt;lint&gt;
    &lt;issue id="NoOp"&gt;
        &lt;option name="pure-getters" value="false" /&gt;
    &lt;/issue&gt;
&lt;/lint&gt;
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

(##) Example

Here is an example of lint warnings produced by this check:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~text
src/Test.kt:3:Warning: This reference is unused: s === o [NoOp]
    s === o                // ERROR 1
    -------
src/Test.kt:4:Warning: This call result is unused: toString [NoOp]
    o.toString()           // ERROR 2
    ------------
src/Test.kt:5:Warning: This reference is unused: length [NoOp]
    s.length               // ERROR 3
      ------
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Here is the source file referenced above:

`src/Test.kt`:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~kotlin linenumbers
class Test {
    fun test(s: String, o: Any) {
       s === o                // ERROR 1
       o.toString()           // ERROR 2
       s.length               // ERROR 3
    }
}
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

You can also visit the
[source code](https://cs.android.com/android-studio/platform/tools/base/+/mirror-goog-studio-main:lint/libs/lint-tests/src/test/java/com/android/tools/lint/checks/NoOpDetectorTest.kt)
for the unit tests for this check to see additional scenarios.

(##) Suppressing

You can suppress false positives using one of the following mechanisms:

* Using a suppression annotation like this on the enclosing
  element:

  ```kt
  // Kotlin
  @Suppress("NoOp")
  fun method() {
     problematicStatement()
  }
  ```

  or

  ```java
  // Java
  @SuppressWarnings("NoOp")
  void method() {
     problematicStatement();
  }
  ```

* Using a suppression comment like this on the line above:

  ```kt
  //noinspection NoOp
  problematicStatement()
  ```

* Using a special `lint.xml` file in the source tree which turns off
  the check in that folder and any sub folder. A simple file might look
  like this:
  ```xml
  &lt;?xml version="1.0" encoding="UTF-8"?&gt;
  &lt;lint&gt;
      &lt;issue id="NoOp" severity="ignore" /&gt;
  &lt;/lint&gt;
  ```
  Instead of `ignore` you can also change the severity here, for
  example from `error` to `warning`. You can find additional
  documentation on how to filter issues by path, regular expression and
  so on
  [here](https://googlesamples.github.io/android-custom-lint-rules/usage/lintxml.md.html).

* In Gradle projects, using the DSL syntax to configure lint. For
  example, you can use something like
  ```gradle
  lintOptions {
      disable 'NoOp'
  }
  ```
  In Android projects this should be nested inside an `android { }`
  block.

* For manual invocations of `lint`, using the `--ignore` flag:
  ```
  $ lint --ignore NoOp ...`
  ```

* Last, but not least, using baselines, as discussed
  [here](https://googlesamples.github.io/android-custom-lint-rules/usage/baselines.md.html).

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